Driving apparatus of light emitting diode and liquid crystal display using the same

Abstract

A driving apparatus of a light emitting diode and a liquid crystal display are disclosed. The driving apparatus of a LED includes a plurality of LED groups in which LEDs are connected in series to each other; a plurality of constant voltage supply units that supplies a constant voltage required to drive a constant current to each of the plurality of LED groups and that outputs the constant voltage in which an output voltage is equal to or lower than an input voltage; and a pulse width modulation signal supply unit that supplies a pulse width modulation signal to each of the constant voltage supply units.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The implementation of this document will be described in detail with reference to the following drawings in which like numerals refer to like elements.

FIG. 1 is a diagram illustrating a driving circuit of a LED for a back light of a liquid crystal display in the related art.

FIG. 2 is a block diagram schematically illustrating a driving circuit of a liquid crystal display.

FIG. 3 is a diagram illustrating a detailed configuration of a driving apparatus of a light emitting diode.

FIG. 4 is a circuit diagram illustrating a detailed configuration of a constant voltage supply unit in the driving apparatus of the light emitting diode shown in FIG. 3.

FIG. 5 is a graph illustrating pulse width modulation signals of the driving apparatus of the light emitting diode.

Claims

1. A driving apparatus for a light emitting diode (LED), comprising: a plurality of light emitting diode groups in which light emitting diodes are connected to each other;a plurality of constant voltage supply units that supplies a constant voltage to drive a constant current to the plurality of light emitting diode groups and that outputs the constant voltage where an output voltage is equal to or lower than an input voltage; anda pulse width modulation signal supply unit that supplies a pulse width modulation signal to respective ones of the plurality of constant voltage supply units.

2. The driving apparatus of claim 1, wherein the light emitting diodes are connected in series to each other.

3. The driving apparatus of claim 1, wherein the plurality of constant voltage supply units comprises: a switching control signal supply unit that supplies a switching control signal;a switching module that is turned on based on a switching control signal supplied from the switching control signal supply unit;an energy storage unit that stores energy supplied through the switching module; anda diode that transfers energy stored in the energy storage unit to each of the plurality of light emitting diode groups.

4. The driving apparatus of claim 3, wherein the plurality of constant voltage supply units further comprises a capacitor.

5. The driving apparatus of claim 3, wherein the plurality of constant voltage supply units further comprises: a current sensing resistor that senses a current transferred to the plurality of light emitting diode groups by an output voltage supplied to each of the plurality of light emitting diode groups; anda current adjusting unit that adjusts a current to a fixed current value.

6. The driving apparatus of claim 3, wherein the switching module comprises a metal oxide semiconductor field effect transistor.

7. The driving apparatus of claim 3, wherein the switching module comprises a bipolar junction transistor.

8. The driving apparatus of claim 3, wherein the energy storage unit comprises an inductor.

9. The driving apparatus of claim 1, wherein the plurality of LED groups comprises a number (n) of light emitting diodes, wherein n is about greater than 2 and about less than 32.

10. A liquid crystal display comprising: a liquid crystal panel; anda driving apparatus of a light emitting diode that illuminates the liquid crystal panel at a rear of the liquid crystal panel,wherein the driving apparatus of the light emitting diode comprises:a plurality of light emitting diode groups in which light emitting diodes are connected to each other;a plurality of constant voltage supply units that supplies a constant voltage to drive a constant current to each of the plurality of light emitting diode groups and that outputs the constant voltage where an output voltage is equal to or lower than an input voltage; anda pulse width modulation signal supply unit that supplies a pulse width modulation signal to respective ones of the plurality of the constant voltage supply units.

11. The liquid crystal display of claim 10, wherein the light emitting diodes are connected in series to each other.

12. The liquid crystal display of claim 10, wherein the plurality of constant voltage supply unit comprises: a switching control signal supply unit that provides a switching control signal;a switching module that is turned on based on a switching control signal supplied from the switching control signal supply;an energy storage unit that stores energy supplied through the switching module; anda diode that transfers energy stored in the energy storage unit to respective ones of the plurality of light emitting diode groups.

13. The liquid crystal display of claim 12, wherein the plurality of constant voltage supply units further comprises a capacitor.

14. The liquid crystal display of claim 12, wherein the plurality of constant voltage supply unit further comprises: a current sensing resistor that senses a current transferred to the respective ones of the plurality of light emitting diode groups by an output voltage supplied to the respective ones of the plurality of light emitting diode groups; anda current adjusting unit that adjusts a current to a fixed current value.

15. A method of driving an apparatus of a light emitting diode (LED) comprising a plurality of light emitting diode groups in which light emitting diodes are connected to each other, the method comprising: supplying a constant voltage required to drive a constant current to respective ones of the plurality of light emitting diode groupsand that outputs the constant voltage in which an output voltage is equal to or lower than an input voltage; andsupplying a pulse width modulation signal to respective ones of the plurality of constant voltage supply units.

16. The method of claim 15, the light emitting diodes are connected in series to each other.

17. The method of claim 15, further comprising: supplying a switching control signal;adjusting a stored amount of energy depending on a turn-on time, based on a switching control signal supplied from the switching control signal supply unit;storing energy supplied through a switching module; andtransferring the stored energy to each of the plurality of light emitting diode groups.

18. The method of claim 15, further comprising reducing a ripple voltage of an output voltage supplied to the plurality of light emitting diode groups.

19. The method of claim 15, further comprising: sensing a current transferred to the plurality of light emitting diode groups by an output voltage supplied to each of the plurality of light emitting diode groups; andadjusting a current sensed through a current sensing resistor to a fixed current value.